The present intention relates in general terms to an air flap for an air-ducting device with at least two ducts, which have a common outlet zone, and in particular to an air flap for a vehicle heating, ventilation and/or air-conditioning system. The two ducts with a common outlet zone can be, for example, the fresh-air or cold-air path, on the one hand, and the warm-air path on the other hand, the heating heat exchanger being arranged in the latter, the common outlet zone often being referred to in this case as a mixing zone, while the air flap in this application is generally referred to as the mixed-air flap.
Currently known mixed-air flaps are generally of the butterfly type and are arranged in such a way in the mixing zone that the warm-air duct is blocked in one end position while, in another position, the fresh-air duct is blocked. In the intermediate positions, the mixed-air flap allows air to pass out of both ducts, depending on its position. In the intermediate positions, the two ducts are connected together both upstream and downstream of the flap in terms of flow, with the result that it is possible not only for the desired mixing of air to take place in the mixing zone but also for each of the air ducts to affect the other owing to the build-up of back-pressure.
Such mixed-air flaps furthermore often lead to unwanted noise and, in some applications, also do not enable the desired clear cross section of the ducts in question to be exposed.
In addition to the above-mentioned mixed-air flaps of the butterfly type, so-called shell-type flaps are known for other applications in the motor-vehicle sector, e.g. for selecting fresh air and recirculated air in air-conditioning systems (DE-A-4228866). These so-called shell-type flaps often lead to noise generation in the closing range and require a considerable amount of installation space, for which reason this type of air flap is seldom used despite the fact that it allows permanent separation of two air ducts ending in a common outlet zone.
There has therefore long been a requirement for an air flap which can prevent mixing of air in ducts upstream of it while being of simple construction, other requirements being that the cross section exposed should be as large as possible in open positions and that noise generation should be minimised in this position.
According to the invention, this object is achieved by an air flap with the features of claim 1. Preferred embodiments are defined in the dependent claims.
In particular, the invention proposes an air flap for an air-ducting device, in particular a vehicle heating, ventilation and/or air-conditioning system, with at least two ducts, which have a common outlet zone, which comprises a region which allows part of the outlet zone to be divided in a sealed manner in each position of the air flap, this region being smaller than the area of the air flap. Mutual interference between the air flows, owing to the build-up of back-pressure for example, can be effectively prevented by using one region for sealing between the two ducts, the dimensioning of this region as only part of the area of the overall flap allowing effective exposure of clear cross sections and low-noise positioning in the open positions.
This region advantageously corresponds essentially to part of the lateral surface of a cylinder, allowing the sealing function to be embodied simply as a contact seal which can be formed by a sealing lip or some other elastically deformable element, for example.
To enable a further reduction in the noise generated as air flows past the air flap, it is possible for this region to be assigned an air guide surface on the side associated with the pivot, it being possible in particular, for this surface preferably to extend essentially in the manner of a chord relative to the lateral surface of the cylinder.
Another factor to be taken into account, apart from noise generation, in the context of heating, ventilation and/or air-conditioning systems, is flow resistance, for which reason the surface of the flap is advantageously designed as an air guide surface which is adapted to the end positions as regards the flow. This enables the flow profile, which differs from case to case, e.g. that in the mixing zone, to be taken into account.
The surface of the air flap can have at least one essentially flat section or, alternatively, can be essentially flat or planar overall. The provision of flat sections makes it possible to block cross sections of air ducts in an effective manner, flush contact with walls of the air-ducting device being made possible in the open positions.
The surface of the air flap is advantageously of essentially S-shaped design in section. By virtue of such a configuration, an advantageous leading edge, on the one hand, and improved contact characteristics in the closed or end positions can be obtained in any position.
To enable even larger cross sections to be exposed, it is advantageous if the surface of the flap is spaced apart from the pivot of the flap. By means of this configuration, the air flap can in some measure be pivoted out of the respective duct in question, in some measure with the swinging movement.
It is furthermore preferred that, in the end positions, the effective area is formed essentially by the region and in each case one adjoining region. The transition between the region and the adjoining regions can form different angles depending on the configuration, and the ratio can also be varied in accordance with the structural requirements.
Finally, it is preferred that a device which influences the air flow, flow velocity and/or the pressure be provided. Such a device can comprise a ramp-shaped guide vane, a guide rib or a partition acting in the manner of a dam gate, either individually or in combination. This configuration is advantageous particularly for those positions of the air flap in which one airflow is considerably less than the other, e.g. in a position close to one of the end positions. Satisfactory mixing of the air flows overall can be achieved in such situations and, in particular, there is also the possibility of achieving particular temperature stratifications or temperature profiles.